chore(compiler-core): reduce unnecessary cache inside v-once (#4112)

packages/compiler-core/__tests__/transforms/vModel.spec.ts

@@ -425,6 +425,18 @@ describe('compiler: transform v-model', () => {
     ).not.toBe(NodeTypes.JS_CACHE_EXPRESSION)
   })
 
+  test('should not cache update handler if it inside v-once', () => {
+    const root = parseWithVModel(
+      '<div v-once><input v-model="foo" /></div>',
+      {
+        prefixIdentifiers: true,
+        cacheHandlers: true
+      }
+    )
+    expect(root.cached).not.toBe(2)
+    expect(root.cached).toBe(1)
+  })
+
   test('should mark update handler dynamic if it refers slot scope variables', () => {
     const root = parseWithVModel(
       '<Comp v-slot="{ foo }"><input v-model="foo.bar"/></Comp>',

packages/compiler-core/__tests__/transforms/vOn.spec.ts

@@ -530,6 +530,15 @@ describe('compiler: transform v-on', () => {
       expect(root.cached).toBe(0)
     })
 
+    test('should not be cached inside v-once', () => {
+      const { root } = parseWithVOn(`<div v-once><div v-on:click="foo"/></div>`, {
+        prefixIdentifiers: true,
+        cacheHandlers: true
+      })
+      expect(root.cached).not.toBe(2)
+      expect(root.cached).toBe(1)
+    })
+
     test('inline function expression handler', () => {
       const { root, node } = parseWithVOn(`<div v-on:click="() => foo()" />`, {
         prefixIdentifiers: true,

packages/compiler-core/__tests__/transforms/vOnce.spec.ts

@@ -80,6 +80,13 @@ describe('compiler: v-once transform', () => {
     expect(generate(root).code).toMatchSnapshot()
   })
 
+  // v-once inside v-once should not be cached
+  test('inside v-once', () => {
+    const root = transformWithOnce(`<div v-once><div v-once/></div>`)
+    expect(root.cached).not.toBe(2)
+    expect(root.cached).toBe(1)
+  })
+
   // cached nodes should be ignored by hoistStatic transform
   test('with hoistStatic: true', () => {
     const root = transformWithOnce(`<div><div v-once /></div>`, {